Solar control coatings having a layer stack of glass/Si3N4/NiCr/Si3N4 are known in the art. Unfortunately, while such layer stacks provide efficient solar control and are overall good coatings, they sometimes are lacking in terms of: (a) corrosion resistance to acid (e.g., HCl boil); (b) mechanical performance such as scratch resistance; and/or (c) thermal stability upon heat treatment for tempering, heat bending, or the like (i.e., ΔE* value(s)).
With respect to such coatings having a layer stack of glass/Si3N4/NiCr/Si3N4, such coatings often do not provide sufficient corrosion resistance to solutions such as acid solutions, especially in monolithic applications. Moreover, the NiCr can become a getter for nitrogen atoms in the neighboring silicon nitride layer(s) during heat treatment (HT), so that diffusion of nitrogen and/or nickel (Ni) can create significant color shifts upon HT. While the use of NiCrN may be used to reduce color shift upon HT, Ni diffusion still occurs upon HT thereby causing chemical and/or thermal instability.
Solar control layers of NbN, ZrN or TiN are known in the art (e.g., see U.S. 2002/0192473 or JP 63-206333). Unfortunately, such metal nitrides have limitations such as reduced deposition rates compared to their respective metallic counterparts. Moreover, they tend to have higher resistivity than their bulk data because of deviation from optimal stoichiometry, and/or high porosity and significant grain-boundary impurities associated with possible columnar growth mode. Moreover, nitrides such as TiN and ZrN tend to have strong golden color which makes color tuning difficult.
Accordingly, there exists a need in the art for a coated article that has improved characteristics with respect to (a) corrosion resistance to acid(s), (b) mechanical durability, (c) thermal stability upon HT, (d) reasonably neutral color, and/or (e) deposition rate, but which still is capable of acceptable solar control (e.g., blocking a reasonable amount of IR and/or UV radiation). It is a purpose of this invention to fulfill at least one of the above-listed needs, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.